This invention relates to an improved biopsy channel for use in the insertion tube of an endoscope and, in particular, to a biopsy channel having improved lubricity, flexibility and strength.
Most biopsy channels found in the prior art are made of vinyl tubing. Vinyl possesses limited lubricity and it is therefore sometimes difficult to pass an instrument such as a biopsy forceps, through the channel when the insertion tube is required to negotiate a short radius, or tight, bend. The vinyl channel, being relatively stiff, further tends to buckle or flatten out along the length of the bend making it more difficult to pass an instrument through the restricted region. The wall of the vinyl channel is usually relatively thick to prevent the channel from collapsing when an internal vacuum is applied to the channel during certain medical procedures. The thick wall again adversely effects the channels ability to accommodate tight bends. A thick walled tube will not deform in specific areas in response to localized pressures normally exerted by rigid instruments, such as biopsy forceps or the like as the instrument is forced through a tight bend. Under certain conditions, the thick walled tube will in fact resist passage of the instrument through the restricted bend region.
Other types of elastomeric materials have been used in the fabrication of biopsy channels in an effort to overcome some of the difficulties associated with vinyl tubes. One such material is a commercially available substance marketed under the tradename Gortex. Although this material exhibits improved lubricity and flexibility, it is permeable and unless treated in some manner will pass air and fluids through its membrane-like channel wall. Similarly, this material lacks body strength and it must be reinforced in some way in order to preserve the integrity of the channel. A biopsy channel utilizing this type of material is disclosed in U.S. Pat. No. 4,279,245 to Takagi et al.